Electrically conductive, optically transparent polymer/carbon nanotube composites

ABSTRACT

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T g ) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of commonly-owned patentapplication Ser. No. 10/288,797, filed Nov. 1, 2002, issued as U.S. Pat.No. 7,588,699 which, pursuant to 35 U.S.C. §119, claimed the benefit ofpriority from provisional patent application having U.S. Ser. No.60/336,109, filed on Nov. 2, 2001, the contents of which areincorporated herein in their entirety.

ORIGIN OF INVENTION

The invention described herein was jointly made by employees of the U.S.Government, contract employees and employees of the National ResearchCouncil, and may be manufactured and used by or for the government forgovernmental purposes without the payment of royalties thereon ortherefor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to methods of preparation thateffectively disperse carbon nanotubes into polymer matrices, and thenovel nanocomposites that result therefrom.

2. Description of the Related Art

Since carbon nanotubes (CNTs) were discovered in 1991 (S. Iijima, Nature354 56, 1991), significant interest has been generated due to theirintrinsic mechanical, electrical, and thermal properties (P. M. Ajayan,Chem. Rev. 99 1787, 1999). Early studies focused on CNT synthesis andtheoretical prediction of physical properties. Due to the recentdevelopment of efficient CNT synthesis (A. Thess et al., Science 273483, 1996) and purification procedures (A. G. Rinzler et al., Appl.Phys. A 67 29, 1998), some applications have been realized. However,these applications have relied on the use of pure CNTs, notnanocomposites. Examples include a carbon nanoprobe in scanning probemicroscopy (S. S. Wong et al., J. Am. Chem. Soc. 120 603, 1998), singlewall carbon nanotube (SWNT) transistor (S. J. Tans et al., Nature 39349, 1998), and field emission display (Q. H. Wang et al., Appl. Phys.Lett. 70 3308, 1997). There have been very few reports on thedevelopment of nanocomposites using CNTs as reinforcing inclusions in apolymer matrix primarily because of the difficulty in dispersing thenanotubes. This difficulty is partially due to the non-reactive surfaceof the CNT. A number of studies have concentrated on the dispersion ofCNTs, but complete dispersion of the CNTs in a polymer matrix has beenelusive due to the intrinsically strong van der Waals attraction betweenadjacent tubes. In practice, attempts to disperse CNTs into a polymermatrix leads to incorporation of agglomerates and/or bundles ofnanotubes that are micron sized in thickness and, consequently, they donot provide the desired and/or predicted property improvements. Most ofthe dispersion related studies have focused on modifying the CNT surfacechemistry. Many researchers have studied the functionalization of CNTwalls and ends. One example is fluorination of CNT surfaces (E. T.Mickelson et al., J. Phys. Chem. 103 4318, 1999), which can subsequentlybe replaced by an alkyl group to improve the solubility in an organicsolvent. Although many researchers have tried to functionalize CNT endsand exterior walls (as a means to increase solubility) by variousapproaches such as electrochemistry and wrapping with a functionalizedpolymer, the solubility of these modified tubes was very limited. Othermethods of CNT modification include acid treatment (i.e. oxidation) anduse of surfactants as a means of improving solubility and compatibilitywith organic polymers. It has been noted that modifications of thenanotube chemical structure may lead to changes in intrinsic propertiessuch as electrical conductivity (X. Gong et al., Chem. Mater., 12 1049,2000). Ultrasonic treatment has also been used as a means to disperseCNTs in a solvent. Upon removal of the sonic force, the tubesagglomerate and settle to the bottom of the liquid.

Individual SWNTs can exhibit electrical conductivity ranging fromsemi-conductor to metallic depending on their chirality, while thedensity is in the same range of most organic polymers (1.33×1.40 g/cm³).In the bulk, they form a pseudo-metal with a conductivity ofapproximately 10⁵ S/cm (Kaiser et al., Physics Reviews B, 57, 14181998). The conductive CNTs have been used as conductive fillers in apolymer matrix to enhance conductivity, however the resultingnanocomposites exhibited little or no transparency in the visible range(400-800 nm). Coleman et al., (Physical Review B, 58, R7492, 1998) andCurran et al., (Advanced Materials, 10, 1091, 1998) reported conjugatedpolymer-CNT composites using multi-wall CNTs, which showed that thepercolation concentration of the CNTs exceeded 5 wt %. The resultingnanocomposites were black with no transparency in the visible region.Shaffer and Windle (Advanced Materials, 11, 937, 1999) reportedconductivity of a multi-wall CNT/poly(vinyl alcohol) composite, whichalso showed percolation above 5 wt % nanotube loading and produced ablack nanocomposite. The same group (J. Sandler, M. S. P. Shaffer, T.Prasse, W. Bauhofer, K. Schulte, and A. H. Windle, Polymer 40, 5967,1999) reported another multi-wall CNT composite with an epoxy, whichachieved percolation below 0.04 wt %. An optical micrograph of theCNT/epoxy composite was reported, which revealed that the CNT phase wasseparated from the epoxy resin, showing several millimeters ofresin-rich domains. The dispersion of CNTs in this material was verypoor. This agglomeration of CNTs in selected areas in the compositecould explain the high conductivity observed since it provides the“shortest path” for the current to travel. Preliminary measurements ofthe conductivity of a CNT/poly(methyl methacrylate) (PMMA) compositewere measured on a fiber (R. Haggenmueller. H. H. Gommans, A. G.Rinzler. J. E. Fischer, and K. I. Winey, Chemical Physics Letters, 330,219, 2000). The level of conductivity was relatively high (1.18×10⁻³S/cm) at 1.3 wt % SWNT loading. However, the optical transparency in thevisible range was not determined for the fiber sample. The mechanicalproperties of these fibers were much less than the predicted value,which implies that the CNTs were not fully dispersed.

The present invention is directed to methods of preparation thatovercome the shortcomings previously experienced with the dispersion ofCNTs in polymer matrices and the novel compositions of matter producedtherefrom. The resulting nanocomposites exhibit electrical conductivity,improved mechanical properties, and thermal stability with highretention of optical transparency in the visible range.

SUMMARY OF THE INVENTION

Based on what has been stated above, it is an objective of the presentinvention to effectively disperse CNTs into polymer matrices. It is afurther objective to prepare novel polymer/CNT nanocomposites andarticles derived therefrom. Methods of preparation that were evaluatedinclude: (1) low shear mixing of a polymer solution with CNTs dispersedin an organic solvent; (2) high shear mixing (e.g., homogenizer orfluidizer) of a polymer solution with CNTs dispersed in an organicsolvent; (3) ultrasonic mixing (e.g., sonic horn at 20-30 kHz for 1-10minutes) of a polymer solution with CNTs dispersed in an organicsolvent; (4) high shear mixing (e.g., homogenizer, fluidizer, or highspeed mechanical stirrer) of a polymer solution with CNTs dispersed inan organic solvent with subsequent ultrasonic mixing (e.g., sonic hornat 20-30 kHz for 1-10 minutes); (5) synthesis of the polymer in thepresence of pre-dispersed CNTs; and (6) synthesis of the polymer in thepresence of pre-dispersed CNTs with simultaneous sonication (e.g., 40-60kHz in a water bath) throughout the entire synthesis process. Methods(4), (5) and (6) are applicable to a variety of polymers that can besynthesized in a solvent in the presence of the CNTs.

The resulting polymer/CNT materials exhibit a unique combination ofproperties that make them useful in a variety of aerospace andterrestrial applications, primarily because of their combination ofimproved mechanical properties, thermal stability, electricalconductivity, and high optical transmission. Examples of spaceapplications include thin film membranes on antennas, second-surfacemirrors, thermal optical coatings, and multi-layer thermal insulation(MLI) blanket materials. For these applications, materials that do notbuild-up electrical charge are preferred. In addition to exhibitingelectrical conductivity, some of these space applications also requirethat the materials have low solar absorptivity and high thermalemissivity. Terrestrial applications include electrically conductivecoatings on a variety of substrates, electrostatic dissipative coatingson electromagnetic displays, coatings for use in luminescent diodes,antistatic fabrics, foams, fibers, threads, clothing, carpeting andother broad goods.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates preparation of an aromatic poly(amide acid)/CNT andpolyimide/CNT nanocomposite.

FIG. 2 illustrates preparation of an aromatic poly(arylene ether)/CNTnanocomposite.

FIG. 3 illustrates preparation of a 0.1 wt % CNT/polyimide nanocompositefrom 1,3-bis(3-aminophenoxy) benzene (APB) and4,4′-perfluoroisopropylidiene dianhydride (6FDA).

FIG. 4 illustrates preparation of a 0.1wt % SWNT/polyimide nanocompositefrom 2,6-bis(3-aminophenoxy) benzonitrile [(β-CN)APB] and3,3′,4,4′-oxydiphthalic dianhydride (ODPA).

FIG. 5 illustrates preparation of a 0.1% wt/wt LA-NT/polyimidenanocomposite from [2,4-bis(3-aminophenoxy)phenyl]diphenylphosphineoxide (APB-PPO) and ODPA.

FIG. 6 illustrates preparation of a 0.2% wt/wt LA-NT/polyimidenanocomposite from APB-PPO and ODPA.

FIG. 7 illustrates preparation of a 0.1% wt/wt CVD-NT-1/polyimidenanocomposite from APB-PPO and ODPA.

FIG. 8 illustrates preparation of a 0.2% wt/wt CVD-NT-1/polyimidenanocomposite from APB-PPO and ODPA.

FIG. 9 illustrates preparation of a 0.1% wt/wt CVD-NT-2/polyimidenanocomposite from APB-PPO and ODPA.

FIG. 10 illustrates preparation of a 0.2% wt/wt CVD-NT-2/polyimidenanocomposite from APB-PPO and ODPA.

FIG. 11 illustrates preparation of a 0.1% wt/wt LA-NT/poly(aryleneether)/SWNT nanocomposite.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves the preparation of polymer/CNT compositeswith a unique combination of properties. The methods of preparationeffectively disperse the CNTs into polymer matrices and overcomeshortcomings of previous efforts to effectively disperse CNTs intopolymers. The methods were successful using both single wall carbonnanotubes (SWNTs) and multi-wall carbon nanotubes (MWNTs). Within thescope of the present invention, the term CNT(s) designates both SWNTsand MWNTs. The resulting nanocomposites exhibit a unique combination ofproperties, such as high retention of optical transparency in thevisible range, electrical conductivity, high mechanical properties, andhigh thermal stability. Appropriate selection of the polymer matrixproduces additional desirable properties such as vacuum ultravioletradiation resistance, atomic oxygen resistance, high T_(g), excellentflexibility and high toughness. Of particular significance is theability to fabricate freestanding films as well as coatings that exhibitan excellent and extremely useful combination of good opticaltransparency, electrical conductivity, high mechanical properties, andthermal stability.

Condensation polymers, such as polyimides, poly(arylene ether)s andpoly(amide acids) and aromatic copolymers such as copolyimides,copoly(arylene ether)s and copoly(amide acids) can be used to preparenanocomposites containing well dispersed CNTs. The methods discussedherein effectively dispersed CNTs into polymer matrices on a nanoscalelevel such that significant improvements in electrical conductivitycould be achieved without significant darkening or reduction in opticaltransmission in the visible region of the resultant nanocomposite. Thefollowing methods of preparation of polymer/CNT nanocomposites wereevaluated: 1) low shear mixing of a polymer solution with CNTs dispersedin an organic solvent; 2) high shear mixing (e.g., homogenizer,fluidizer, or high-speed mechanical stirrer) of a polymer solution withCNTs dispersed in an organic solvent; 3) ultrasonic mixing (e.g., sonichorn at 20-30 kHz for approximately 1-10 minutes) of a polymer solutionwith CNTs dispersed in an organic solvent; 4) high shear mixing (e.g.,homogenizer, fluidizer, or high-speed mechanical stirrer) of a polymersolution with CNTs dispersed in an organic solvent with subsequentultrasonic mixing (e.g., sonic horn at 20-30 kHz for approximately 1-10minutes); 5) synthesis of the polymer in the presence of pre-dispersedCNTs; and 6) synthesis of the polymer in the presence of pre-dispersedCNTs with simultaneous sonication (e.g., water bath operating at 40 kHz)throughout the entire synthesis process. The effects of these differentmethods of preparation on electrical conductivity and opticaltransmission were investigated.

Preparation of Carbon Nanotube Dispersion

Two different types of CNTs were dispersed. The CNTs differed in theirmethod of preparation [either laser ablation (LA) or chemical vapordeposition (CVD)], as well as the average lengths and diameters of thetubes. The LA CNTs were single wall carbon nanotubes (SWNTs) and wereobtained from Tubes@Rice as purified dispersions in toluene. The CVDCNTs were multi-wall carbon nanotubes (MWNTs) and were obtained fromNanolab, Inc. CNT dispersions were prepared by placing the CNTs into anorganic solvent, preferably at concentrations of less than 1 weightpercent (wt %). Although concentrations of less than 1 wt % arepreferred, concentrations of up to about 3% may be used for thin films(i.e., less than approximately 5 μm thick) while still achievingretention of optical transparency. The liquid to disperse the CNTs waschosen based on its compatibility and solvating characteristics with themonomers and polymer of interest. Preferably, polar aprotic solventswere selected that were also compatible with the polymers to besynthesized. The CNT dispersion was mixed mechanically, as appropriate,with a high-speed, high-shear instrument (e.g., homogenizer, fluidizer,or high-speed mechanical stirrer) and was subsequently placed in a glassvessel and immersed in an ultrasonic water bath operating at 40-60 kHzfor several 1-10 hours to achieve initial dispersion.

Selection of Polymers

Predominately aromatic and conjugated polymers are generally preferredfor use in the preparation of polymer/CNT nanocomposites for long-termaerospace applications owing to their high-temperature resistance andhigh durabilities. Representative aromatic polymers and copolymers,representing the poly(amide acid), polyimide and poly(arylene ether)families, were selected based upon their solubility in several polaraprotic solvents of choice and their ability to be synthesized in thepresence of the CNTs without any deleterious effects on molecular weightbuild-up as evidenced by a noticeable increase in solution viscosity. Insome cases, target polymers with polar groups such as carbonyl, cyano,phosphine oxide, sulfone and others or conjugated polymers were selectedto provide additional compatibility with CNTs. In some cases, polymerswith very high optical transmission (i.e. greater than approximately85%) at 500 nm were selected to demonstrate this approach. Particularlygood results, with respect to degree of dispersion, were obtained witharomatic polymers containing polar groups.

Methods of Preparation of Composites

Several methods of preparing polymer/CNT composites were evaluated andare described in detail below.

Method (1) (Low Shear Mixing)

Low shear mixing of a pre-synthesized high molecular weight aromaticpolymer solution with CNTs dispersed in an organic solvent was conductedby preparing a polymer solution in a solvent and subsequently adding theCNT dispersion (prepared as previously described). A mechanical stirrerwas used to mix the two components. This approach typically resulted inpoor mixing and poor dispersion. The CNTs separated from solution uponremoval of the mechanical agitation. The resulting film and/or coatingwere black in color and exhibited poor retention of optical transmission(i.e., less than approximately 35% retention of optical transmission) at500 nm. Optical microscopic examination of the nanocomposite film showedthe presence of agglomerates of CNT bundles indicating poor dispersion.

Method (2) (High Shear Mixing)

High shear mixing (e.g., using homogenizer, fluidizer, or high-speedmechanical stirrer) of a pre-synthesized high molecular weight aromaticpolymer solution with CNTs dispersed in an organic solvent was conductedby preparing a polymer solution in a solvent and subsequently adding theCNT dispersion (prepared as previously described). A flat bottomgenerator equipped with a homogenizer operating at about 7500revolutions per minute (rpm) was used for approximately 20 minutes tomix the two components. Experiments were undertaken to study the effectof homogenization time on level of dispersion. Longer homogenizationtimes (>1 hour) did not provide significant improvement in mixing anddispersion as compared to shorter times (<1 hour). This approachtypically resulted in better mixing and dispersion as compared to Method(1), but the resulting nanocomposite films and/or coatings were blackand exhibited poor retention of optical transmission (i.e. less thanapproximately 35% retention of optical transmission) at 500 nm. Opticalmicroscopic examination of the nanocomposite film showed the presence ofagglomerates of CNT bundles indicating poor dispersion.

Method (3) (Ultrasonic Mixing with Sonic Horn)

Ultrasonic mixing of a pre-synthesized high molecular weight aromaticpolymer solution with CNTs dispersed in an organic solvent was conductedby preparing a polymer solution in a solvent and subsequently adding theCNT dispersion (prepared as previously described). A high power sonichorn equipped with a 13 mm probe operating at 20 kHz was used to mix thetwo components. Experiments were undertaken to study the effect ofultrasonic treatment time on level of dispersion. Longer ultrasonictreatment times (>10 min.) did not provide significant improvement inmixing and dispersion as compared to shorter ultrasonic treatment times(<10 min.). This high power ultrasonic treatment appeared to causesignificant damage to the polymer as evidenced by a noticeable decreasein solution viscosity. This observation suggests that chemical bondcleavage is occurring that subsequently leads to a reduction inmolecular weight. The possibility also exists that this high powerultrasonic treatment may cause damage (i.e., introduction of defectsites through carbon-carbon bond cleavage) to the CNTs. Modification ofthe chemical structure of CNTs is known to cause bulk property changes,thus this method was deemed undesirable. Nanocomposite films and/orcoatings prepared from solutions that received relatively shortexposures (<10 min.) to the high power sonic horn treatment exhibitedimprovements in electrical conductivity of 10-12 orders of magnitude;however the nanocomposite films and/or coatings exhibited moderateretention of optical transparency (i.e., 35-50% retention of opticaltransmission) in the visible range. Optical microscopic examination ofthe nanocomposite film showed the presence of agglomerates of CNTbundles indicating poor dispersion. Based on a qualitative assessment,the nanocomposite film prepared via this method exhibited marginallyimproved dispersion relative to the nanocomposite films prepared viaMethods (1) and (2).

Method (4) (High Shear and Ultrasonic Mixing Using Sonic Horn)

A combination of high shear mixing and ultrasonic treatment wasconducted by initially preparing an aromatic polymer solution in asolvent and subsequently adding the CNT dispersion (prepared aspreviously described). A homogenizer was subsequently used to mix thedispersion, followed by ultrasonic treatment with a high power sonichorn operated at 20 kHz. The times of each treatment were varied, but nosignificant differences in dispersion were apparent. This combinationtreatment generally gave better dispersion than one single componentmixing. Nanocomposite films and/or coatings with 0.1 wt % CNT exhibitedimprovements in electrical conductivity of 10-12 orders of magnitudecompared to a pristine polymer film. However, the nanocomposite filmsand/or coatings exhibited moderate retention of optical transparency(i.e., 35-50% retention of optical transmission) at 500 nm. Opticalmicroscopic examination of the nanocomposite film showed the presence ofagglomerates of CNT bundles, indicating poor dispersion. Based on aqualitative assessment, the nanocomposite film prepared via this methodexhibited marginally improved dispersion relative to the nanocompositefilms prepared via Methods (1) and (2).

Method (5) (Synthesis of the Polymer in the Presence of Pre-DispersedCNTs)

Synthesis of an aromatic polymer in the presence of the CNTs wasconducted by pre-dispersing the CNTs in the solvent of interest andsubsequently adding the monomers. In the case of the poly(amide acid)sand polyimides, the diamine component was added first to thepredispersed CNTs and allowed to be stirred until dissolved. Thedianhydride component was subsequently added as a solid and theprogression of the polymerization was readily observable by asignificant build-up in solution viscosity. The re-aggregation among theCNTs are inhibited and/or minimized due to the high viscosity of thesolution, which preserves the state of CNT dispersion during furtherrequired processing. The polymerization was allowed to proceed underconditions analogous to those generally used for the particular polymertype using a mechanical stirrer (i.e., under low shear). Nanocompositefilms and/or coatings with 0.1 wt % CNT exhibited improvements inelectrical conductivity of 10-12 orders of magnitude compared to apristine polymer film and a high retention of optical transparency(greater than 50%) at 500 nm. Optical microscopic examination of thenanocomposite film showed the presence of CNT bundles and agglomeratesof bundles. However, the bundles were of a smaller size than thoseobserved in nanocomposite films prepared by Methods (1)-(4). Based on aqualitative assessment, the nanocomposite film prepared via this methodexhibited significantly improved dispersion relative to thenanocomposite films prepared via Methods (1)-(4). Optionally, thesolution obtained by Method (5) may be filtered to remove extraneousparticles or large agglomerates of CNT bundles.

Method (6) (Synthesis of the Polymer in the Presence of Pre-dispersedCNTs with Simultaneous Ultrasonic Treatment)

A combination method of preparation involving synthesis of the polymerin the presence of the CNTs while simultaneously applying ultrasonictreatment using a low power water bath operating at 40 kHz throughoutthe entire synthesis process was investigated. This method involvedsynthesis of the polymer in the presence of pre-dispersed CNTs asdescribed in Method (5), but the reaction vessel was immersed in anultrasonic bath throughout the entire synthesis. It should be noted thatin contrast to Methods (3) and (4), which used a high power sonic hornoperating at 20 kHz (100-750 Watt/cm²), the ultrasonic bath operates ata much lower level of power (less than 10 Watt/cm²) and at a higherfrequency (40 kHz). Based on the observed increase in solution viscosity(indicating high molecular weight polymer formation) and microscopicanalysis of the nanocomposite films, the use of the ultrasonic bathoperating at 40 kHz did not cause any observable degradation of theCNTs, nor did it affect the formation of high molecular weight polymer.Nanocomposite films and/or coatings with 0.1 wt % CNT exhibitedimprovements in electrical conductivity of 10-12 orders of magnitudecompared to a pristine polymer film and a high retention of opticaltransparency (i.e., greater than about 50%) at 500 nm. Opticalmicroscopic examination of the nanocomposite film showed the presence ofCNT bundles and agglomerates of bundles. However, the bundles were of asmaller size than those observed in nanocomposite films prepared bymethods (1)-(4). Based on a qualitative assessment, the nanocompositefilm prepared via this method exhibited significantly improveddispersion relative to the nanocomposite films prepared via Methods(1)-(4). Optionally, the solution obtained by Method (6) may be filteredto remove extraneous particles or large agglomerates of CNT bundles.

Performing synthesis of the polymers [i.e., Methods (5) and (6)] in thepresence of the CNTs provided significant improvement in the dispersionof the CNTs, provided the smallest decrease in optical transmission,provided an equal or better electrical conductivity compared to apristine polymer film and provided a stable solution. Attempts to mix apre-synthesized high molecular weight aromatic polymer solution with aCNT dispersion was unsuccessful in achieving good dispersion and highretention of optical transmission. Methods (5) and (6) are applicable tovarious condensation polymers such as poly(amide acid), polyimide andpoly(arylene ether)/CNT nanocomposites as shown in FIGS. 1 and 2. FIG. 1illustrates the preparation of polyimide and poly(amide acid))/CNTnanocomposites, wherein Ar and Ar′ can be any aromatic moiety. FIG. 2illustrates the preparation of poly(arylene ether)/CNT composites,wherein Ar″ represents any aromatic moiety, X represents a leaving groupsuch as a halogen, nitro or other suitable group and Ar′″ represents anyelectron withdrawing group or ring system.

EXAMPLES

The following specific examples are provided for illustrative purposesand do not serve to limit the scope of the invention.

Example 1A Preparation of 0.1 wt % CNT/polyimide nanocomposite from1,3-bis(3-aminophenoxy)benzene (APB) and 4,4′-perfluoroisopropylidienedianhydride (6FDA) by Method (6)

FIG. 3 illustrates preparation of 0.1 wt % LA-NT/polyimide nanocompositefrom APB and 6 FDA by Method (6).

Purified SWNTs obtained from Tubes@Rice as a dispersion in toluene wereused as the conductive inclusions. A dilute SWNT solution, typicallyapproximately 0.01% weight/volume (w/v) in N,N-dimethylformamide (DMF),was prepared by replacing the toluene with DMF by centrifuging anddecanting several (typically three) times. Pure CNT powders could alsobe used, eliminating the previous step. The dilute SWNT solution washomogenized for 10 min. and sonicated for 1 hour in a ultrasonic bathoperating at 40 kHz. If a higher power sonic bath is used, sonicationtime can be reduced depending on the power. Sonication time should bealso adjusted depending on the quality of CNTs. The sonicated SWNTsolution (2 mL, 0.01 g of the solid SWNT) was transferred into a 100 mLthree neck round bottom flask equipped with a mechanical stirrer,nitrogen gas inlet, and drying tube outlet filled with calcium sulfate.The flask was immersed in the ultrasonic bath throughout the entiresynthesis procedure. APB (3.9569 g, 1.353×10⁻² mol) was added into theflask along with 20 mL of DMF while stirring under sonication. Afterapproximately 30 min. of stirring the SWNT and diamine mixture, 6FDA(6.0432 g, 1.360×10⁻² mol) was added along with additional 30.5 mL ofDMF with stirring under sonication. The dark mixture was stirred in thesonic bath overnight, approximately 12 hours, to give a 0.1% by weightSWNT/poly(amide acid) solution. During the course of the reaction, anoticeable increase in solution viscosity was observed. Theconcentration of the SWNT/poly(amide acid) was 16% solids (w/w) in DMF.The SWNT/poly(amide acid) solution was treated with acetic anhydride(4.1983 g, 4.080×10⁻² mol) and pyridine (3.2273 g, 1.360×10⁻² mol) toeffect imidization. The resulting solution was cast onto plate glass andplaced in a dry air box for 24 hours to give a tack-free film. This filmwas thermally treated (to remove solvent) for 1 hour each at 110, 170,210 and 250° C. in a forced air oven. The film was removed from theglass and characterized.

Example 1B

Film was prepared in a manner identical to that described for EXAMPLE1A, except that the SWNT concentration in the polyimide was 0.2% byweight.

Example 1C

Film was prepared in a manner identical to that described for EXAMPLE1A, except that the SWNT concentration in the polyimide was 0.5% byweight.

Example 1D

Film was prepared in a manner identical to that described for EXAMPLE1A, except that the SWNT concentration in the polyimide was 1.0% byweight.

Example 1E

Film was prepared in a manner to that described for EXAMPLE 1D, exceptthat Method (1) was employed instead of Method (6).

Example 2 Preparation of 0.1 wt % LA-NT/polyimide nanocomposite from2,6-bis(3-aminophenoxy)benzonitrile [(β-CN)APB] and3,3′,4,4′-oxydiphthalic dianhydride (ODPA) by Method (6)

FIG. 4 illustrates the preparation of 0.1 wt % LA-NT/polyimidenanocomposite from 2,6-bis(3-aminophenoxy) benzonitrile [(β-CN)APB] andODPA by Method (6).

Purified SWNTs obtained from Tubes@Rice as a dispersion in toluene wereused as the conductive inclusions. A dilute SWNT solution, generallyabout 0.01% w/v in N,N-dimethylacetamide (DMAc), was prepared byreplacing the toluene with DMAc by centrifuging and decanting several(typically three) times. The dilute SWNT solution was homogenized for 10min. and sonicated for 1 hour in an ultrasonic bath operating at 40 kHz.The SWNT solution (2 mL, 0.01 g of the solid SWNT) was transferred intoa 100 mL three neck round bottom flask equipped with a mechanicalstirrer, nitrogen gas inlet, and drying tube outlet filled with calciumsulfate. The flask was immersed in the ultrasonic bath during the entirereaction. (β-CN)APB, (5.0776 g, 1.60×10⁻² mol) was subsequently added tothe flask along with 20 mL of DMAc while stirring under sonication.After approximately 30 min., ODPA (4.9635 g, 1.60×10⁻² mol) was addedalong with an additional 30.5 mL of DMAc. The dark mixture was stirredunder sonication overnight, approximately 12 hours, to give a 0.1 wt %SWNT/poly(amide acid) solution. During the course of the reaction, anoticeable increase in solution viscosity was observed. Theconcentration of the solid SWNT/poly(amide acid) was 16% (w/w) in DMAc.The SWNT/poly(amide acid) solution was treated with acetic anhydride(4.1983 g, 4.080×10⁻² mol) and pyridine (3.2273 g, 1.360×10⁻² mol) toeffect imidization. The resulting solution was cast onto plate glass andplaced in a dry air box for 24 hours to give a tack-free film. This filmwas thermally treated (to remove solvent) for 1 hour each at 50, 150,200 and 240° C. in a nitrogen oven. The film was removed from the glassand characterized.

Example 3 Preparation of a 0.1% wt/'wt LA-NT/polyimide nanocompositefrom [2,4-bis(3-aminophenoxy)phenyl]diphenylphosphine oxide (APB-PPO)and ODPA by Method (5)

FIG. 5 illustrates preparation of a 0.1% wt/wt LA-NT/polyimidenanocomposite APB-PPO and ODPA by Method (5).

A glass vial containing 0.0060 g of nanotubes and 10 mL DMF was placedin an ultrasonic bath operating at 40 kHz for periods ranging from 16 to24 hours. A 100 mL three neck round bottom flask equipped with amechanical stirrer, nitrogen gas inlet, and drying tube filled withcalcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³ mole) andDMF (5.0 mL). Once the diamine dissolved, the DMF/SWNT mixture was addedand the resulting mixture was stirred for 20 mins. ODPA (2.3164 g,7.467×10⁻³ mole) was added along with additional DMF (8.2 mL) to give asolution with a concentration of 20% (w/w) solids and a nanotubeconcentration of 0.1% wt/m. The mixture was stirred overnight at roomtemperature under a nitrogen atmosphere. During the course of thereaction a noticeable increase in solution viscosity was observed. Thepoly(amide acid) was chemically imidized by the addition of 2.31 g ofacetic anhydride and 1.77 g of pyridine. The reaction mixture wasstirred at room temperature overnight under a nitrogen atmosphere. Thepolyimide/nanomaterial mixture was precipitated in a blender containingdeionized water, filtered, washed with excess water and dried in avacuum oven at 150° C. overnight to afford a light gray, fibrousmaterial. A solution prepared from DMF or chloroform (20% solids w/w)was cast onto plate glass and allowed to dry to a tack-free state in adust-free chamber. The film on the glass plate was placed in a forcedair oven for 1 hour each at 100, 150, 175 and 225° C. to remove solvent.The film was subsequently removed from the glass and characterized.

Example 4 Preparation of a 0.2% wt/wt LA-NT/polyimide nanocomposite fromAPB-PPO and ODPA via Method (5)

FIG. 6 illustrates preparation of a 0.2% wt/wt LA-NT/polyimidenanocomposite from APB-PPO and ODPA via method (5).

A glass vial containing 0.0120 g of LA-NT nanotubes and 10 mL of DMF wasplaced in an ultrasonic bath operating at 40 kHz for periods rangingfrom 16 to 24 hours. A 100 mL three neck round bottom flask equippedwith a mechanical stirrer, nitrogen gas inlet, and drying tube filledwith calcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³mole) and DMF (5.0 mL). Once the diamine dissolved, the DMF/SWNT mixturewas added and the resulting mixture was stirred for 20 min. ODPA (2.3164g, 7.467×10⁻³ mole) was added along with additional DMF (8.2 mL) to givea solution with a concentration of 20% (w/w) solids and a nanotubeconcentration of 0.2% wt/wt. The mixture was stirred overnight at roomtemperature under a nitrogen atmosphere. The poly(amide acid) waschemically imidized by the addition of 2.31 g of acetic anhydride and1.77 g of pyridine. The reaction mixture was stirred at room temperatureovernight, approximately 12 hours, under a nitrogen atmosphere. Duringthe course of the reaction a noticeable increase in solution viscositywas observed. The polyimide/SWNT mixture was precipitated in a blendercontaining deionized water, filtered, washed with excess water and driedin a vacuum oven at 150° C. overnight to afford a light gray, fibrousmaterial. A solution prepared from DMF or chloroform (20% solids w/w)was cast onto plate glass and allowed to dry to a tack-free state in adust-free chamber. The film on the glass plate was placed in a forcedair oven for 1 hour each at 100, 150, 175 and 225° C. to remove solvent.The film was subsequently removed from the glass and characterized.

Example 5 Preparation of a 0.1% wt/wt CVD-NT-1/polyimide nanocompositefrom APB-PPO and ODPA by Method (5)

FIG. 7 illustrates the preparation of a 0.1% wt/wt CVD-NT-1/polyimidenanocomposite from APB-PPO and ODPA by Method (5).

A glass vial containing 0.0060 g of CVD-NT-1 nanotubes and 10 mL of DMFwas placed in an ultrasonic bath at 40 kHz for periods ranging from 16to 24 hours. A 100 ml, three neck round bottom flask equipped with amechanical stirrer, nitrogen gas inlet, and drying tube filled withcalcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³ mole) andDMF (5.0 mL). Once the diamine dissolved, the DMF/CNT mixture was addedand the resulting mixture was stirred for 20 min. ODPA (2.3164 g,7.467×10⁻³ mole) was added along with additional DMF (8.2 mL) to give asolution with a concentration of 20% (w/w) solids and a nanotubeconcentration of 0.1% wt/wt. The mixture was stirred overnight at roomtemperature under a nitrogen atmosphere. During the course of thereaction, a noticeable increase in solution viscosity was observed. Thepoly(amide acid) was chemically imidized by the addition of 2.31 g ofacetic anhydride and 1.77 g of pyridine. The reaction mixture wasstirred at room temperature overnight # under a nitrogen atmosphere. Thepolyimide/CNT mixture was precipitated in a blender containing deionizedwater, filtered, washed with excess water and dried in a vacuum oven at150° C. overnight to afford a light gray, fibrous material. A solutionprepared from DMF or chloroform (20% solids w/w) was cast onto plateglass and allowed to dry to a tack-free state in a dust-free chamber.The film on the glass plate was placed in a forced air oven for 1 houreach at 100, 150, 175 and 225° C. to remove solvent. The film wassubsequently removed from the glass and characterized.

Example 6 Preparation of a 0.2% wt/wt CVD-NT-1/polyimide nanocompositefrom APB-PPO and ODPA by Method (5)

FIG. 8 illustrates the preparation of a 0.2% wt/wt CVD-NT-1/polyimidenanocomposite from APB-PPO and ODPA by Method (5).

A glass vial containing 0.0120 g of CVD-NT-1 nanotubes and 10 mL of DMFwas placed in an ultrasonic bath operating at 40 kHz for periods rangingfrom 16 to 24 hours. A 100 mL three neck round bottom flask equippedwith a mechanical stirrer, nitrogen gas inlet, and drying tube filledwith calcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³mole) and DMF (5.0 mL). Once the diamine dissolved, the DMF/CNT mixturewas added and the resulting mixture was stirred for 20 min. ODPA (2.3164g, 7.467×10⁻³ mole) was added along with additional DMF (8.2 mL) to givea solution with a concentration of 20% (w/w) solids and a nanotubeconcentration of 0.2% wt/wt. The mixture was stirred overnight at roomtemperature under a nitrogen atmosphere. During the course of thereaction, a noticeable increase in solution viscosity was observed. Thepoly(amide acid) was chemically imidized by the addition of 2.31 g ofacetic anhydride and 1.77 g of pyridine. The reaction mixture wasstirred at room temperature overnight, approximately 12 hours, under anitrogen atmosphere. The polyimide/CNT solution was precipitated in ablender containing deionized water, filtered, washed with excess waterand dried in a vacuum oven at 150° C. overnight to afford a light gray,fibrous material. A solution prepared from DMF or chloroform (20% solidsw/w) was cast onto plate glass and allowed to dry to a tack-free statein a dust-free chamber. The film on the glass plate was placed in aforced air oven for 1 hour each at 100, 150, 175 and 225° C. to removesolvent. The film was subsequently removed from the glass andcharacterized.

Example 7 Preparation of a 0.1% wt/wt CVD-NT-2/polyimide nanocompositefrom APB-PPO and ODPA by Method (5)

FIG. 9 illustrates the preparation of a 0.1% wt/wt CVD-NT-2/polyimidenanocomposite from APB-PPO and ODPA by Method (5).

A glass vial containing 0.0060 g of CVD-NT-2 nanotubes and 10 mL of DMFwas placed in an ultrasonic bath operating at 40 kHz for periods rangingfrom 16 to 24 hours. A 100 mL three neck round bottom flask equippedwith a mechanical stirrer, nitrogen gas inlet, and drying tube filledwith calcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³mole) and DMF (5.0 mL). Once the diamine dissolved, the DMF/CNT mixturewas added and the resulting mixture was stirred for 20 minutes. ODPA(2.3164 g, 7.467×10⁻³ mole) was added along with additional DMF (8.2 mL)to give a solution with a concentration of 20% (w/w) solids and ananotube concentration of 0.1% wt/wt. The mixture was stirred overnight,approximately 12 hours, at room temperature under a nitrogen atmosphere.During the course of the reaction, a noticeable increase in solutionviscosity was observed. The poly(amide acid) was chemically imidized bythe addition of 2.31 g of acetic anhydride and 1.77 g of pyridine. Thereaction mixture was stirred at room temperature overnight # under anitrogen atmosphere. The polyimide/CNT solution was precipitated in ablender containing deionized water, filtered, washed with excess waterand dried in a vacuum oven at 150° C. overnight to afford a light gray,fibrous material. A solution prepared from DMF or chloroform (20% solidsw/w) was cast onto plate glass and allowed to dry to a tack-free statein a dust-free chamber. The film on the glass plate was placed in aforced air oven for one hour each at 100, 150, 175 and 225° C. to removesolvent. The film was subsequently removed from the glass andcharacterized.

Example 8 Preparation of a 0.2% wt/wt CVD-NT-2/polyimide nanocompositefrom APB-PPO and ODPA by Method (5)

FIG. 10 illustrates preparation of a 0.2% wt/wt CVD-NT-2/polyimidenanocomposite from APB-PPO and ODPA by Method (5).

A glass vial containing 0.0120 g of CVD-NT-2 nanotubes and 10 mL of DMFwas placed in an ultrasonic bath operating at 40 kHz for periods rangingfrom 16 to 24 hours. A 100 mL three neck round bottom flask equippedwith a mechanical stirrer, nitrogen gas inlet, and drying tube filledwith calcium sulfate was charged with APB-PPO (3.6776 g, 7.467×10⁻³mole) and DMF (5.0 mL). Once the diamine dissolved, the DMF/nanomaterialmixture was added and the resulting mixture was stirred for 20 minODPA(2.3164 g, 7.467×10⁻³ mole) was added along with additional DMF (8.2 mL)to give a solution with a concentration of 20% (w/w) solids and ananotube concentration of 0.2% wt/wt. The mixture was stirred overnight,approximately 12 hours, at room temperature under a nitrogen atmosphere.During the course of the reaction, a noticeable increase in solutionviscosity was observed. The poly(amide acid) was chemically imidized bythe addition of 2.31 g of acetic anhydride and 1.77 g of pyridine. Thereaction mixture was stirred at room temperature overnight,approximately 12 hours, under a nitrogen atmosphere. The polyimide/CNTsolution was precipitated in a blender containing deionized water,filtered, washed with excess water and dried in a vacuum oven at 150° C.overnight to afford a light gray, fibrous material. A solution preparedfrom DMF or chloroform (20% solids w/w) was cast onto plate glass andallowed to dry to a tack-free state in a dust-free chamber. The film onthe glass plate was placed in a forced air oven for one hour each at100, 150, 175 and 225° C. to remove solvent. The film was subsequentlyremoved from the glass and characterized.

Example 9 Preparation of a 0.1% wt/wt. LA-NT/poly(arylene ether)/SWNTnanocomposite by Method (5)

FIG. 11 illustrates the preparation of a 0.1% wt/wt LA-NT/poly(aryleneether)/SWNT nanocomposite by Method (5).

A 100 mL three-necked round bottom flask equipped with a mechanicalstirrer, nitrogen inlet and a Dean-Stark trap topped with a condenserwas charged with 1,3-bis(4-fluorobenzoyl)benzene (2.0000 g, 6.2052×10⁻³mol), 4,4′-isopropylieienediphenol (1.4166 g, 6.2052×10⁻³ mol),single-wall carbon nanotube (from Tubes@Rice) suspension 0.0034 g,sonicated at 40 kHz for 18 hours in 5.0 g N-methyl-2-pyrrolidinone(NMP), potassium carbonate (1.03 g), toluene (10 mL) and 8.7 g NMP. Themixture was stirred under nitrogen and water was removed via azeotropeat approximately 135° C. for about 16 hours. The toluene wassubsequently removed and the remaining mixture was heated at 170° C. for6 hours. The viscous mixture was cooled to room temperature and thenpoured into a 10% aqueous acetic acid solution. A gray fibrousprecipitate was collected via filtration and washed with excess water.The solid was dried in a vacuum oven at 150° C. for 4 hours. A solutionprepared from NMP (20% solids w/w) was cast onto plate glass and allowedto dry to a tack-free state in a dust-free chamber. The film on theglass plate was placed in a forced air oven for 1 hour each at 100, 150,175 and 250° C. to remove solvent. The film was subsequently removedfrom the glass and characterized. A 27 μm thick film exhibited a T_(g)of 250° C. and exhibited an optical transparency at 500 nm of 63%.

Example 10 Preparation of 0.1 wt % CNT/PMMA nanocomposite from methylmethacrylate (MMA) monomers by Method (6)

Purified SWNTs obtained from Tubes@Rice were used as the conductiveinclusions. A dilute SWNT solution, typically approximately 0.01%weight/weight (w/w) in N,N-dimethylformamide (DMF), was prepared. Thedilute SWNT solution was homogenized for 10 min and sonicated for onehour in an ultrasonic bath operating at 40 kHz. The sonicated SWNTsolution (2 mL, 0.01 g of the solid SWNT) was transferred into a 100 mLthree neck round bottom flask equipped with a mechanical stirrer,nitrogen gas inlet, and drying tube outlet filled with calcium sulfate.The flask was immersed in the 80° C. ultrasonic bath throughout theentire synthesis procedure. MMA (10 g, xmol) was added into the flaskalong with 40 mL of DMF while stirring under sonication at 80° C. After30 min of stirring the SWNT and MMA mixture, AIBN (0.04188 g) and1-dodecanethiol (20 ml) were added with stirring under sonication as aninitiator and a chain extender, respectively. The dark mixture wasstirred in the sonic bath six hours to give a 0.1% by weight SWNT/PMMAsolution. During the course of the reaction, a noticeable increase insolution viscosity was observed. The concentration of the SWNT/PMMA was20% solids (w/w) in DMF. The SWNT/PMMA solution was precipitated inmethanol with a high-speed mixer. The precipitates were filtered with anaspirator thoroughly with distilled water. A gray powder was collectedand dried in an vacuum oven at 60° C. The dried powder was re-dissolvedin DMF and cast onto plate glass and placed in a dry air box for 24hours to give a tack-free film. This film was thermally treated (toremove solvent) for six hours in a vacuum oven at 60° C. The film wasremoved from the glass and characterized. The nanocomposite films(SWNT/PMMA) exhibited high relative retention of optical transmission at500 nm (>50% at 0.1 wt % SWNT loading) while exhibiting improvements inelectrical conductivities of 10-12 orders of magnitude compared to thepristine polymer film.

The above examples are provided for illustrative purposes. In additionto the specific condensation and addition polymers described herein,other addition and condensation polymers may be used, includingpolyamides, polyesters, polycarbonates, vinyl polymers, polyethylene,polyacrylonitrile, poly(vinyl chloride), polystyrene, poly(vinylacetate), polytetrafluoroethylene, polyisprene, polyurethane, andpoly(methyl metahcrylate)/polystyrene copolymer.

Characterization

Differential scanning calorimetry (DSC) was conducted on a ShimadzuDSC-50 thermal analyzer. The glass transition temperature (T_(g)) wastaken as the inflection point of the ΔT versus temperature curve at aheating rate of 10° C./min on thin film samples. UV/VIS spectra wereobtained on thin films using a Perkin-Elmer Lambda 900 UV/VIS/NIRspectrophotometer. Thin-film tensile properties were determinedaccording to ASTM D882 using four specimens per test condition.Thermogravimetric analysis (TGA) was performed on a Seiko Model 200/220instrument on film samples at a heating rate of 2.5° C. min⁻¹ in airand/or nitrogen at a flow rate of 15 cm³ min⁻¹. Conductivitymeasurements were performed according to ASTM D257 using a Keithley 8009Resistivity Test Fixture and a Keithley 6517 Electrometer.Homogenization was carried out using PowerGen Model 35 or a PowerGen.Model 700 homogenizer at speeds ranging from 5,000 to 30,000 rpm.Optionally a fluidizer, such as a M-10Y High Pressure Microfluidizerfrom WIC Corp. (Newton, Mass.) could be used. Solar absorptivities weremeasured on a Aztek Model LPSR-300 spectroreflectometer withmeasurements taken between 250 to 2800 nm with a vapor depositedaluminum on Kapton® as a reflective reference. An Aztek Temp 2000AInfrared reflectometer was used to measure the thermal emissivity.Ultrasonication was carried out using a Ultrasonik 57× ultrasonicatorwater bath operating at 40 kHz or with a ultrasonic horn (VCX-750,Sonics and Materials. Inc.) equipped with a 13 millimeter probe.Purified, laser ablated singe wall carbon nanotubes (LA-NT) were used asreceived from Tubes@Rice, Rice University, Houston, Tex. Chemical vapordeposition multi-wall carbon nanotubes (CVD-NT) were used as receivedfrom Nanolab, Inc., Watertown, Mass. Optical microscopy was performed onan Olympus BH-2 microscope. Elemental analysis was performed by DesertAnalytics, Tucson, Ariz.

The nanocomposite films were characterized for optical, electrical andthermal properties. CNTs were subjected to elemental analysis prior touse. The results are summarized in Table 1. Characterization of thenanocomposite films described in EXAMPLES 1A-1E are presented in Tables2 and 3. All of these samples were prepared using LA purified SWNTsobtained from Tubes@Rice.

TABLE 1 Elemental analysis of CNTs CNT Carbon, % Hydrogen, % Iron, %Nickel, % Cobalt, % LA-NT 78.2 0.94 0.06 1.45 1.54 Single wall CVD-NT-196.0 <0.05 1.0 0.002 <0.001 Multi-wall CVD-NT-2 97.0 <0.05 1.5 0.002<0.001 Multi-wall

The polymer matrix was prepared from APB and 6FDA. The control film wasof comparable thickness or thinner than that of the nanocomposite films.The data in Table 2 indicates that at SWNT weight loadings of 0.1 to1.0%, the transmission at 500 nm as determined by UV/VIS spectroscopyindicated a relative retention from less than 1% up to 80%. Thenanocomposite film prepared via Method (1) exhibited by far the lowestretention of optical transmission (less than 1%). The nanocompositefilms prepared via Method (6) exhibited significantly higher relativeretention of optical transmission at 500 nm ranging from 38-80% whileexhibiting improvements in electrical conductivities of 10-12 orders ofmagnitude compared to the pristine polymer film. Of particular note isthe nanocomposite film designated as EXAMPLE 1A, which contained 0.1 wt% SWNT and exhibited high retention of optical transmission (80%) whileexhibiting a volume conductivity of 10⁻⁸ S/cm. When the amount of SWNTwas increased five-fold (EXAMPLE 1C), the nanocomposite still exhibiteda high retention of optical transmission and an increase in volumeconductivity of 11 orders of magnitude compared to the control. Thetemperature of 5% weight loss as determined by dynamic TGA increasedwith increasing SWNT concentration (Table 3) suggesting that theincorporation of SWNTs did not have a significant effect on thermalstability as measured by this technique.

TABLE 2 Optical and electrical properties of select nanocompositefilms¹. UV/VIS Optical SWNT (500 nm) Trans- Loading, Trans- missionConductivity Sample Film² Weight % mission % Retention, % σ_(v) ³, S/cmAPB/6FDA 0 85 — 6.3 × 10⁻¹⁸  EXAMPLE 1A 0.1 68 80 1 × 10⁻⁸ EXAMPLE 1B0.2 62 66 1 × 10⁻⁷ EXAMPLE 1C 0.5 54 64 2 × 10⁻⁷ EXAMPLE 1D 1.0 32 38>10⁻⁵ EXAMPLE 1E 1.0 <1 <1 >10⁻⁵ ¹Films were prepared by Method (6)except for EXAMPLE 1E, which was prepared by Method (1). All films wereprepared using LA purified SWNTs (LA-NT) from Tubes @Rice. ²UV/VIStransmission was normalized at 34 μm. ³σ_(v) (S/cm) = volumeconductivity, S: Siemens = ohm⁻¹

Thermal emissivity (ε) and solar absorptivity (α) measurements are alsoshown in Table 3. In general, the addition of CNTs to the polyimidematerial increased both ε and α. Dynamic mechanical data shown in Table4 show that modulus increased with increasing nanotube concentration,with up to a 60% improvement at 1.0 vol % SWNT loading level. The tan δpeak decreased and shifted up 10° C. with SWNT incorporation at 1.0 vol% as seen in Table 4, which suggests that CNT reinforcement made thenanocomposite more elastic and thermally more stable by increasing theglass transition temperature.

TABLE 3 Temperature of 5% weight loss of nanocomposite films by TGA¹SWNT Temp. of 5% Solar Thermal Loading, Weight Loss, absorptivityemissivity Sample Film Weight % ° C. (α) (ε) APB/6FDA 0 444 0.068 0.525EXAMPLE 1A 0.1 461 0.268 0.578 EXAMPLE 1B 0.2 474 0.398 0.614 EXAMPLE 1C0.5 481 0.362 0.620 EXAMPLE 1D 1.0 479 0.478 0.652 ¹By dynamic TGA at aheating rate of 2.5° C./min. in air after holding 30 min. at 100° C.

TABLE 4 Dynamic Mechanical Data Sample Film Tan δ Max, ° C. Storagemodulus (GPa) APB/6FDA 214 8.5 × 10⁸ EXAMPLE 1A 213 9.2 × 10⁸ EXAMPLE 1C214 1.2 × 10⁹ EXAMPLE 1D 224 1.4 × 10⁹

Another series of 0.1 and 0.2 wt % nanocomposite films were preparedfrom the polyimide derived from APB-PPO and ODPA and three differenttypes of CNTs. Method (5) was used for the preparation of thenanocomposite films described in EXAMPLES 3-9. The nanotubes differed intheir method of preparation (either LA or CVD) as well as the averagelengths and diameters of the tubes. In addition, LA-NT are single wallcarbon nanotubes (SWNTs) and CVD-NT-1 and CVD-NT-2 are multi-wall carbonnanotubes (MWNTs). Table 5 lists the types, sources and approximatedimensions of the nanotubes used in the preparation of nanocompositefilms described in EXAMPLES 3-8.

TABLE 5 Nanotube Designations, Source and Approximate Dimensions AverageAverage Nanotube ID Production Diameter, Nanotube Length, (Type) Methodnm Source μm LA-NT Laser ablation 1.2-1.6 Tubes@Rice ~3 (SWNT) CVD-NT-1CVD <20 Nanolab, Inc. <1 (MWNT) CVD-NT-2 CVD 10-20 Nanolab, Inc. <20(MWNT)

Table 6 lists physical properties of the nanocomposite films, such asT_(g) and thin film mechanical properties. The T_(g) ranged from 187 to212° C. The films exhibited room temperature tensile strengths andmoduli from 77 to 99 MPa and 2.8 to 3.3 GPa, respectively. Theelongations at break ranged from 3.1 to 4.9%. These values arecomparable to other aromatic polyimides. The polyimide/CNT nanocompositefilms exhibited reductions in T_(g) of 5-25° C., comparable tensilestrengths (except for EXAMPLE 6), increased tensile moduli andcomparable or slightly lower elongations to break.

Imidized thin film samples were measured for optical transparency usingUV/VIS spectroscopy. The results are presented in Table 7. The retentionof optical transparency at 500 nm ranged from 52 to 89%. It is wellknown that for these polyimide films, the optical transmission isdependent upon film thickness such that increasing film thicknessresults in a decrease in optical transmission. As shown in Table 7, thefilms thicknesses of the nanocomposite films were comparable or slightlygreater than that of the control. Thus it is reasonable to compare theresults directly without normalization. “High”, “moderate”, and “poor”retention of optical transparency are defined herein to mean greaterthan 50%, 35% to 50%, and less than 35%, respectively.

TABLE 6 Thin Film Tensile Properties at Room Temperature Tensile TensileSample Film, T_(g), Strength, Mod., Elong. @ (CNT conc., wt %) ° C. MPaGPa Break, % APB-PPO/ODPA (0.0) 212 97 2.8 4.7 EXAMPLE 3 (0.1) 187 883.2 3.5 EXAMPLE 5 (0.1) 205 99 3.3 4.2 EXAMPLE 7 (0.1) 206 90 3.1 4.0EXAMPLE 4 (0.2) 200 94 3.2 4.9 EXAMPLE 6 (0.2) 207 77 3.0 3.1 EXAMPLE 8(0.2) 199 — — —

TABLE 7 Optical Transparency of Polyimide/CNT Nanocomposite FilmsRelative CNT Trans- Retention of Film Loading, parency @ Optical Trans-Thickness, Sample film Weight % 500 nm, % parency, % μm APB-PPO/ODPA 085 — 25 EXAMPLE 3 0.1 76 89 32 EXAMPLE 5 0.1 66 78 32 EXAMPLE 7 0.1 4856 27 EXAMPLE 4 0.2 75 88 25 EXAMPLE 6 0.2 44 52 32

Thermal emissivity (ε) and solar absorptivity (α) measurements are shownin Table 8. In general, the addition of CNTs to the polyimide materialincreased both ε and α. The solar absorptivity increased depending uponCNT type, for example the samples with the laser ablated nanotubes(SWNTs, EXAMPLES 3 and 4) exhibited the lowest increase while thechemical vapor deposited nanotubes (MWNTs, EXAMPLES 5 and 6) exhibitedthe largest increase.

As mentioned above for optical transmission, α and ε are also dependentupon film thickness. As shown in Table 8, the nanocomposite filmthicknesses were comparable or slightly greater than that of thecontrol. Thus it is reasonable to compare the results directly withoutnormalization. For some space applications, the increase in solarabsorptivity exhibited by EXAMPLES 3 and 4 would not be detrimental. Allsamples exhibited increases in thermal emissivity which for many spaceapplications is desirable. The term “optically transparent” is definedherein to mean the relative retention of greater than 50% of opticaltransparency (relative to a control film of comparable thickness) asmeasured by UV/VIS spectroscopy at a wavelength of 500 μm. The term“electrically conductive” is defined herein to mean exhibiting a surfaceconductivity ranging from less than 10⁻⁵ S/cm to 10⁻¹² S/cm.

TABLE 8 Solar Absorptivity and Thermal Emissivity of Polyimide/CNTNanocomposite Films Film Sample film, Thermal Solar Thickness, (CNTconc., wt %) Emissivity (ε) Absorptivity (α) μm APB-PPO/ODPA (0.0) 0.5600.049 25 EXAMPLE 3 (0.1) 0.579 0.142 32 EXAMPLE 5 (0.1) 0.641 0.253 32EXAMPLE 7 (0.1) 0.703 0.362 27 EXAMPLE 4 (0.2) 0.609 0.151 25 EXAMPLE 6(0.2) 0.614 0.443 32

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations maybe readily ascertainable by those skilled in the art and may be madeherein without departing from the spirit and scope of the presentinvention as defined by the following claims.

1. An electrically conductive, optically transparent poly (amideacid)/carbon nanotube nanocomposite, comprising a carbon nanotube and apoly(amide acid), wherein the poly(amide acid) is

wherein Ar is selected from the group consisting of

wherein Ar′ is selected from the group consisting of

wherein the number average molecular weight of the poly(amide acid) canrange from approximately 700 g/mole to approximately 100,000 g/mole; andwherein the poly(amide acid) is selected from the group consisting ofendcapped and unendcapped.
 2. An electrically conductive, opticallytransparent polyimide/carbon nanotube nanocomposite comprising a carbonnanotube and a polyimide, wherein the polyimide is

wherein Ar is selected from the group consisting of

wherein Ar′ is selected from the group consisting of

wherein the number average molecular weight of the polyimide is betweenapproximately 700 g/mole and approximately 100,000 g/mole; and whereinthe polyimide is selected from the group consisting of endcapped andunendcapped.
 3. An electrically conductive, optically transparentpoly(arylene ether)/carbon nanotube nanocomposite comprising a carbonnanotube and a poly(arylene ether), wherein the poly(arylene ether) is

O—Ar″—O—Ar′″

wherein Ar″ is

wherein Ar′″ is

wherein the number average molecular weight of the poly(arylene ether)is between approximately 700 g/mole to approximately 100,000 g/mole;wherein the poly(arylene ether) is selected from the group consisting ofendcapped and unendcapped.
 4. A nanocomposite product prepared from thenanocomposite of claim 1, wherein said product is in a form selectedfrom the group consisting of a film, fiber, foam, coating, adhesive,molding and paste.
 5. A nanocomposite product prepared from thenanocomposite of claim 2, wherein said product is in a form selectedfrom the group consisting of a film, fiber, foam, coating, adhesive,molding and paste.
 6. A nanocomposite product prepared from thenanocomposite of claim 3, wherein said product is in a form selectedfrom the group consisting of a film, fiber, foam, coating, adhesive,molding and paste.